Octree-based animated geometry compression

Geometry compression is the compression of the 3D geometric data that provides a computer graphics system with the scene description necessary to render images. Geometric data is quite large and, therefore, needs effective compression methods to decrease the transmission and storage requirements. A large amount of research has been focused on static geometry compression, but only limited research has addressed animated geometry compression , the compression of temporal sequences of geometric data. The goal of this thesis is to represent 3D animation sequences with a reduced set of motion vectors that take advantage of the large data coherence in space and time. An octree-based motion representation method is proposed. In this approach, a small set of motion vectors are generated for each frame by accessing two consecutive frames at a time. These motion vectors represent the differential motion from the previous frame to the current frame. They are used to predict the vertex positions for each frame. The octree motion representation process generates a hierarchical octree structure for each frame in the sequence. Based on this approach, a hybrid coding method is proposed that combines the octree-based approach and delta coding method. Given the same threshold requirement, the hybrid approach performs better than the octree only approach in terms of compression ratio. Both the octree and hybrid approaches can represent 3D animated sequences with high compression factors while maintaining reasonable quality. These two approaches are easy to implement and have a low cost encoding process and a fast decoding process, which make them very suitable for real time application.